Macular degeneration, which is generally agerelated, affects a central region of the retina known as the macula. Macular degeneration can lead to a gradual or rapid loss of vision to the level of 20/200 or less. It may affect, for example, only about 1/4 to 4 square millimeters of the macula, thereby leaving 95 to 99 percent of the retina unaffected. Accordingly, central vision, such as for reading and watching television, can be lost while peripheral vision remains relatively intact.
Vision problems for the patient are compounded if macular degeneration is also accompanied by cataracts on the natural lens of the affected individual. One way of dealing with this compounded vision problem is disclosed in Donn et al U.S. Pat. No. 4,710,197. The disclosed approach is to replace the cataractic natural lens of the eye with a negative intraocular lens and to employ a single, positive lens element on a spectacle frame in combination with the intraocular lens (IOL). A positive or negative contact lens may also be used in this system to further correct the patient's vision.
Another approach is disclosed in Portney U.S. Pat. No. 5,030,231. This patent discloses an IOL with a negative IOL portion and bi-element spectacles serving as a positive lens to direct light toward the negative lens portion of the IOL.
It is often desirable to minimize the vertex distance, i.e., the spacing between the outer surface of the eye and the spectacle lens. A large vertex distance reduces the field of fixation, i.e., the maximum angle within which the eye can move and still see an object clearly and tends to make the spectacles less comfortable to wear and not aesthetically pleasing. A large vertex distance also tends to draw attention to the visual handicap of the wearer. A telephoto lens system as described in U.S. application Ser. No. 730,471 filed on Jul. 16, 1991, now U.S. Pat. No. 5,196,028 can be used to reduce the vertex distance.